The present invention relates generally to automotive service equipment incorporating vehicle wheel turn plates and slip plates, such as vehicle support systems and vehicle lift racks, and in particular, to vehicle wheel turn plates and slip plates configured with automatic centering and locking mechanisms which may be manually or automatically controlled during vehicle service procedures.
Typically, movable surfaces commonly referred to as turn plates and slip plates are placed on the vehicle support system surface on which the vehicle undergoing an alignment procedure is parked, such as a lift runway, as shown in FIG. 1. A turn plate is typically a round plate mounted on a bearing surface, flush with the surface of the vehicle support system. The turn plate permits the steered wheels of a stationary vehicle to be steered from side to side without requiring lifting of the vehicle, and simultaneously permits limited motion in a horizontal plane. A slip plate is similar in configuration, but is generally rectangular, and permits only motion in the horizontal plane, without permitting any rotational movement. These movable surfaces are commonly utilized in order to prevent the vehicle suspension from binding during an alignment adjustment process. Prior to driving a vehicle over the vehicle support surface, and at certain times before and during the measurement of a vehicle suspension system, these movable surfaces must be locked into position to prevent unintentional movement of the vehicle.
For example, during a conventional vehicle wheel alignment procedure, the vehicle is driven onto the vehicle support system with the movable surfaces in a locked configuration. Next, sensors are mounted to the vehicle wheels, and the sensors compensated before actual vehicle alignment measurements are acquired. The compensation procedure is required to eliminate errors in alignment angle measurements resulting from runout of the vehicle wheel, the wheel adaptor, or wheel alignment sensor mounting shaft. The compensation procedure can be performed by rotating the vehicle wheels with the vehicle raised off the runway surface, or alternatively, by rolling the vehicle over a limited range on the runway surface with the wheel alignment sensors attached to the wheels, i.e. “rolling compensation.”
To carry out the procedure for rolling compensation, it is required that the vehicle be rolled backwards off the turn plates approximately 10-20 inches and then rolled forward so that it is returned to the original starting position. Prior to rolling the vehicle, the turn plates and slip plates over which the vehicle will roll must be in the locked position. Often, a device is used to “bridge” a gap between the runway surface and the edge of each turn plate, permitting the vehicle to roll easier.
Following the compensation procedure, the bridge, if present, is either removed or placed in a lowered position to avoid interfering with the range of motion of the turn plate, and the turn plate and slip plate are unlocked from their stationary positions. The alignment measurements and any corrective procedures are then carried out in a conventional manner. Once the alignment procedures have been completed the movable surfaces must again be locked into a stationary configuration before the vehicle may be driven off the vehicle support system.
Movable surfaces such as turn plates and slip plates may be either manually operated or automatically operated. Conventional designs for manually operated turn plates and slip plates require an operator to manually lock the movable surface in place, and typically rely upon the placement and removal of pins to lock the plates in place.
Automatically operated turn plates and slip plates rely on pneumatic cylinders to pneumatically lock the turn plates and slip plates. Two companies are known to produce pneumatically locked turn plates and slip plates, Omer S.p.A. of Italy, and Otto Nuβbaum GmbH & Co. KG of Germany. These designs employ pneumatic cylinders to push the slip plates toward the longitudinal centerline of the vehicle lift rack or supporting surface in response to an operator command, locking them in place. However, the pneumatic cylinders do not center the slip plates on the longitudinal centerlines of each associated runway. A disadvantage to this design is that the slip plates must be narrower than the runway. If not, the locked slip plates will extend over the inner edge of the lift rack runway and possibly interfere with the movement of centrally disposed jacking elements configured for lifting the vehicle above the lift rack runway surfaces.
Accordingly, it would be advantageous to develop an automatic mechanism for simultaneously locking the turn plates and slip plates of a vehicle support system against planar and rotational movement, and for centering the locked turn plates and slip plates on the longitudinal centerline of the associated vehicle support system runways. It would be further advantageous to provide an operator with either one-touch control for simultaneously locking and unlocking all turn plates and slip plates associated with a vehicle support system, or alternatively, controlling the automatic mechanism through a vehicle service system computer such as a vehicle wheel alignment system, thereby reducing the number of times an operated is required to circle the vehicle during an alignment procedure.